Electromagnetic absorption of a pinned Wigner crystal at finite temperatures

Abstract

We investigate the microwave absorption of a pinned, two-dimensional Wigner crystal in a strong magnetic field at finite temperatures. Using a model of a uniform commensurate pinning potential, we analyze thermal broadening of the electromagnetic absorption resonance. Surprisingly, we find that the pinning resonance peak should remain sharp even when the temperature is comparable or greater than the peak frequency. This result agrees qualitatively with recent experimental observations of the ac conductivity in two-dimensional hole systems in a magnetically induced insulating state. It is shown, in analogy with Kohn's theorem, that the electron-electron interaction does not affect the response of a harmonically pinned Wigner crystal to a spatially uniform external field at any temperature. We thus focus on anharmonicity in the pinning potential as a source of broadening. Using a 1/N expansion technique, we show that the broadening is introduced through the self-energy corrections to the magnetophonon Green's functions.

21 pages, 9 eps figures

References in corpus (2)

• Dynamical properties of the pinned Wigner crystal
• 1/N expansion for two-dimensional quantum ferromagnets

Cited by in corpus (8)

• Pinned Wigner Crystals
• Dynamical response of a weakly pinned two-dimensional Wigner crystal
• Dynamical response of a pinned two-dimensional Wigner crystal
• Zero field Wigner crystal
• Crossover between localized states and pinned Wigner crystal in high-mobility n-GaAs/AlGaAs heterostructures near filling factor $\nu =1$
• Melting of Wigner crystal in high-mobility $n$-GaAs/AlGaAs heterostructures at filling factors $0.18>\nu >0.125$: Acoustic studies
• Replica study of pinned bubble crystals
• Wigner crystal in a two-dimensional electron system in the vicinity of filling factor 1/5: Acoustic studies